There are many critical factors the pilot of an aircraft must consider when determining if the aircraft is safe for take-off. One of those factors is identifying the proper weight and center of gravity for the aircraft. Hereinafter, “aircraft weight and center of gravity” will be referred to as “aircraft weight.”
Typical aircraft used in day-to-day airline operations are commonly supported by a plurality of compressible, telescopic landing gear struts. These landing gear struts contain pressurized hydraulic fluid and nitrogen gas. The weight of the aircraft rests upon and is supported by theses “pockets” of compressed nitrogen gas, within the landing gear struts.
When measuring the weight of an aircraft, the aircraft weight can be classified into two types. The first type of weight is commonly referred to as “sprung weight.” The sprung weight is the vast majority of the aircraft weight and is located/suspended above the “pockets” of compressed nitrogen gas, within the telescopic landing gear strut. The second type of weight is a much smaller amount of the total weight and is commonly referred to as “unsprung weight.” Unsprung weight is the weight of the landing gear components which are located below the pockets of compressed nitrogen gas. The unsprung weight is virtually a constant and unchanging weight. Brake wear and tire wear are the only variations to unsprung weight; and in the consideration of the aircraft total weight, is a very minimal amount.
In the initial design and certification of aircraft, there are three different aircraft structural weight limitations which are established. These three weight limitations are predicated upon the structural design of the aircraft. Prior to each flight the pilot of the aircraft must assure throughout the operation of any flight, the aircraft remains within these certified structural weight limitations. The highest of these weight limitations is the “Maximum-Ramp Weight.” The Max-Ramp Weight limitation is the heaviest weight that the aircraft is allowed to taxi. This weight is slightly higher than the aircraft “Maximum Take-off Weight.” The higher Ramp Weight is to allow for the weight of fuel-burn, used for the aircraft to travel from the airport terminal gate to the starting point of the aircraft take-off roll. The Maximum Take-off Weight is the heaviest weight at which the aircraft is allowed to take-off. The third weight limitation is the “Maximum Landing Weight” limitation, which is the heaviest weight at which and aircraft is designed for landing.
In a search of the prior art, there are numerous, existing onboard aircraft weight and balance systems which measure aircraft weight. Research of the prior art to determine aircraft automatic aircraft weight and balance systems can be divided into two basic strategies. One strategy is the method of measuring the pressure within the landing gear strut. The other being the method of measuring the amount of landing gear axle bending/deflection, as the aircraft weight increases. Both of these approaches are well documented and reference may be made to United States patents:
U.S. Pat. #3,584,503 SenourU.S. Pat. #5,548,517 NanceU.S. Pat. #3,701,279 HarrisU.S. Pat. #6,128,951 NanceU.S. Pat. #5,214,586 NanceU.S. Pat. #6,237,406 NanceU.S. Pat. #5,521,827 LindbergU.S. Pat. #6,237,407 Nance
U.S. Pat. No. 6,032,090 VonBose teaches the additional art of measuring landing gear strut friction which also uses the measurement of aircraft vertical acceleration in measuring aircraft landing gear strut seal friction and United States Patent Application Publication # US/2006/0220918-A1 Stockwell teaches the additional art of rotating landing gear strut seals in a means to reduce landing gear strut seal friction, which is used to reduce frictional errors, in the measurement of aircraft weight.
The prior art described by these patents explain mechanical apparatus added to the landing gear strut which measure the weight of the aircraft, but none of these prior art designs offer a “non-human interfacing” to determine any particular segment of the aircraft operation, to further determine an optimum time to initiate an fully automated function, for determining the aircraft weight measurement.
The technology described in this application offers improvements to these prior art aircraft weight and balance systems. Where each of the existing systems offer aircraft weight measurements upon the physical and manual request by a human, this new technology offers methods of an artificial intelligence within the aircraft weight measuring system's software, which can be applied to any of the prior art systems. Aircraft weight and aircraft location upon and around the airport can be determined, as well as determining the optimum time to make an automated request for a measured, recorded and then stored aircraft weight determination.
In further defining the optimum time for requesting aircraft weight determination, a review of typical airline operations can herein be examined. In most of today's airline operations, the deteitnination of aircraft weight is accomplished by a method of determining the number of passengers which are to board onto the aircraft, and multiplying that number of passengers times an assumed average passenger weight value. Such average passenger weight has been determined by previous population weight survey data. In continuation of the process to determine aircraft weight, there is a determination as to the amount of weight for the luggage and bags which each passenger checked at the airline ticket counter, to then be loaded onto the aircraft and stored within the aircraft cargo compartment. An “average bag weight” for each particular size and shape of each piece of luggage is determined, and that determined average bag weight is multiplied times the number of bags loaded onto the aircraft, to determine this total cargo weight. On larger aircraft, which transport the much heavier palletized cargo, each pallet is actually weighed, and that measured weight is used in the aircraft weight calculations. Aircraft fuel is measured by gallons and pumped into the aircraft fuel tanks. Onboard aircraft fuel indicators further convert the number of gallons pumped, into the pounds of weight added to the aircraft. Aircraft fuel indicators incorporate a density compensation feature which can have errors as high as 2% of that fuel weight. With a long-haul aircraft such as may travel from the US to Europe, the weight of the fuel can be up to 25% of the entire weight of the aircraft.
This aircraft weight calculation is referred to as the “dispatch weight” of the aircraft. Sometimes this term “dispatch weight” is referred to as the “primary dispatch weight and center of gravity.”
Weeks before an airline flight is scheduled to dispatch, the airline begins the process to plan the anticipated loads and weight for that flight. The development of this “planned load” involves the tracking of ticket and cargo sales for that particular flight segment. Additionally, weather and wind patterns, both current and historic are reviewed to offer recommendations as to the amount of fuel which should be needed and will be loaded onto the aircraft, for this particular flight.
Where a “measured” aircraft weight would be the most accurate means to determine aircraft weight, having an accurate measured weight can cause operational problems for an airline. As a scheduled airline flight draws near to its scheduled departure time, having weight data based on calculations of historical weight survey data (as opposed to an accurate measured weight) insures that the airline's “planned weight” will always match the airline's “dispatch weight.” Having a planned aircraft weight value that does not exactly match a dispatch weight value (which would be mechanically measured just after the aircraft has completed the loading process) can cause extremely difficult operational problems for the airline, just minutes prior to the time of the aircraft departure. Regulatory authorities who administer the safe operation of such airlines would not allow such weight discrepancies to remain unresolved, and thus not allow that aircraft to dispatch without determining the discrepancy. By not having the more accurate aircraft weight data made available, just before and aircraft is ready to take-off, is operationally of more benefit to the airline procedures, as opposed to having an accurately measured aircraft weight available for the primary dispatch of the aircraft.
Though the more accurate aircraft weight and center of gravity measurement could be a disruptive factor for primary dispatch, the measured weight information is a valuable tool in the measuring of aircraft performance. Aircraft and engine performance is related to the amount of fuel burned on a particular flight. The amount of fuel which is burned relates to the amount of weight which that aircraft carries up to altitudes in excess of 30,000 feet.
Many of today's airlines are initiating programs to improve overall operational efficiency. A commonly used program is called FOQA (Flight Operation Quality Assurance). These FOQA programs monitor multiple streams of data and onboard aircraft sensor information to measure items such as airspeed, rate of altitude change, rate of fuel consumption and other factors which affect the performance of the aircraft.
Having the ability to measure and record the aircraft weight information without the participation of aircraft flight and/or ground crew, and further storing the aircraft weight data for use in measuring aircraft performance, is of benefit in measuring aircraft performance. Additionally, having validations of aircraft center of gravity loading trends can be used in future operations, to better plan aircraft loading patterns; that a more optimum aircraft center of gravity could be achieved. Having an aircraft fly with its center of gravity located at a more aft position, within its center of gravity limitations allows the aircraft to reduce aerodynamic drag, and thus burn less fuel on each flight.
Creating the process for which an automated method to capture measured aircraft weight and balance, which utilizes sensors on each landing gear strut, and an onboard computer which monitors those sensors measurements, with the ability to recognize when an aircraft is at rest; being loaded with passengers, cargo and fuel; which has left the departure gate as is beginning to taxi towards the departure runway; which recognizes that additional weight (such as deicing fluid) is being applied to the aircraft; and is further proceeding along a runway for take-off; and later completes a landing event; begins its post landing taxi towards an arrival gate; and finally comes to rest at the airport terminal gate; will allow for aircraft weight information to be independently measured and stored, for future use.
The method described herein is applicable as an improvement to existing prior art aircraft weight and balance measuring systems, to make the prior art functional for features which they were not initially intended.
Further, the method described herein eliminates the need for any human interface in the process of initiating a request for an aircraft weight determination, but instead offers an artificial intelligence feature within the software of any of a number of weight and balance system computers, wherein this new method determines when the weight measurement should be made. Aircraft weight increases and decreases are monitored to detect patterns of change over defined periods of time. The detected patterns will create triggers as to when an aircraft weight measurement should be made and recorded.